What "toxicity" meansThis is a featured page

What does non-toxic mean? What does toxic really mean?
Toxicity has nothing to do with morbidity - or causing disease. It is a measure of how much it takes to kill a healthy 150 pound man. Please read on.....

Toxic Hazard

Toxicity:
Toxicity Ratings “are based on mortality, not morbidity, i.e., it is really a lethality rating. In general a clinically significant illness may be expected after doses of about one-tenth the probable lethal dose (the later being reflected in the numerical toxicity rating). Unless otherwise noted, each rating is based on the acute toxicity of a single dose when taken by mouth or gavage. Other dose regimens and other routes of administration are not represented by the rating. The toxicity rating reflects an estimate of the probable or mean lethal dose, not the minimal fatal dose. Perhaps because of personal idiosyncrasy or hypersensitivity or predisposing disease, minimal lethal doses recorded in the clinical literature are usually considerably lower than those implied by the current ratings. With only a few compounds are clinical data adequate to establish a toxicity rating. Toxicity ratings followed by interrogation points are based on obviously inadequate data; some represent no more than “guesstimates”. Common units of measure are used to describe lethal doses for a male adult of average size (body weight of 150 lbs or 70 kg). For patients who are heavier or lighter, probable lethal doses are proportionately larger or smaller. While we appreciate that infants and children are not simply small adults, reliable clinical data are so scarce that we are forced to assume that lethal doses are proportional to body weight irrespective of age.

Rating System
Toxicity Rating Probable Lethal Dose (human)
(For a 150 pound male)
6 “super” toxic a taste (less than 7 drops)
5 extremely toxic between 7 drops and 1 teaspoonful
4 very toxic between 1 tsp and 1 ounce
3 moderately toxic between 1 oz and 1 pint (or 1 lb)
2 slightly toxic between 1 pt and 1 quart
1 practically non-toxic more than 1 quart

Reference:
Clinical Toxicology of Commercial Products, Third Edition

Gleason, Gosselin, Hodge, Smith
The Williams & Wilkins Co. 1969


Factors that Affect the Toxicity of Products

General Principles of Toxicology
To evaluate the toxic nature of a substance, scientists have developed several general criteria for consideration, including:

Nature of the Toxic Substance. Toxicologists try to determine the characteristics that render a chemical toxic. Individual molecules may not be toxic in their native states but become toxic after being metabolized. The size and shape of particles may affect their toxicity.

Dose and Length of Exposure. These parameters, together with rates of metabolism and excretion, determine what quantity of a substance is actually affecting the body. A given substance may be toxic in high doses but nontoxic under conditions of chronic low-dose exposure. (Remember: Toxicity has nothing to do with morbidity or the causing of disease. It is a mortality rating).

Route of Exposure.
The pathway by which a toxicant enters the body (e.g., skin, eye, lungs, or gastrointestinal tract) affects its toxicity.
The amount of absorption, ability of the toxicant to combine with native molecules at the entry point (e.g., heavy metals with skin collagen), vulnerability of sensitive areas (e.g., lining of the lung), and condition of the organ at time of contact (e.g., pH and content of the stomach) all play a role in subsequent toxicity.

Species Affected. Toxicants exhibit different levels and effects of toxicity depending on the species on which it is tested. (Species - this is in regard to animal testing and the results - it may vary depending on the species. When testing iin laboratories there are many factors involved in choosing the species to be used in the test including which species is most similar to humans for the subject matter being tested, cost involved, etc.)

Age. Susceptibility to a toxicant varies with age—the young and the old generally being the most susceptible.

State of Health. The health status of an individual, including the presence of disease, can greatly affect toxicity response. For example, people with asthma may suffer adverse effects from substances that do no harm to most individuals.

Individual Susceptibility. Host factors such as genetic predisposition affect the response of an individual to a toxicant.

Presence of Other Agents. Toxicology often involves evaluating one substance in isolation, yet the body is seldom exposed to agents in this manner. Knowledge about toxic effects of multiple substances is not well-developed because of the practical limitations of testing the infinite number of combinations.

Adaptation/Tolerance. Biological adaptation to a toxicant often occurs when chronically low doses are presented. Adaptation/tolerance must be factored into evaluating the range of individual responsiveness to a toxicant.

SOURCE:
U.S. Office of Technology Assessment, 1992
Congress of the United States
Identifying and Controlling Pulmonary Toxicants
OTA-BP-BA-91 NTIS order #PB92-193457
Full Report: http://www.princeton.edu/~ota/ns20/alpha_f.html
Select Letter I


To jump to Chapter 3, page 3, box 3A:
http://www.princeton.edu/~ota/disk1/1992/9223/922305.PDF (
Box 3A, page 3)



Return to Terminology
Return to Home Page





There are no threads for this page.  Be the first to start a new thread.